High quality diamond formation by electron temperature control in methane-hydrogen plasma

We report a new method for the nucleation and growth of diamonds by employing an electron-temperature control technique in CH₄/H₂ radio frequency glow discharge plasma under a low gas pressure of 100 mTorr. The electron temperature in the plasma is controlled under constant gas pressure in a range from 0.5 to 2.5 eV continuously by changing the open area of the slits situated around a grid that is kept at the floating potential. It is observed that the film quality is changed in accordance with the variation of electron temperature, and we can produce high quality diamond in a low electron temperature plasma, even though usually only graphite film is deposited, unless the electron temperature is controlled.